640643635620349 has 2 divisors, whose sum is σ = 640643635620350. Its totient is φ = 640643635620348.

The previous prime is 640643635620323. The next prime is 640643635620431. The reversal of 640643635620349 is 943026536346046.

It is a happy number.

640643635620349 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 441616859561124 + 199026776059225 = 21014682^2 + 14107685^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640643635620349 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640643635720349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320321817810174 + 320321817810175.

It is an arithmetic number, because the mean of its divisors is an integer number (320321817810175).

Almost surely, 2^{640643635620349} is an apocalyptic number.

It is an amenable number.

640643635620349 is a deficient number, since it is larger than the sum of its proper divisors (1).

640643635620349 is an equidigital number, since it uses as much as digits as its factorization.

640643635620349 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 201553920, while the sum is 61.

The spelling of 640643635620349 in words is "six hundred forty trillion, six hundred forty-three billion, six hundred thirty-five million, six hundred twenty thousand, three hundred forty-nine".